The Supreme Court’s conservative majority Tuesday signaled that it remains strongly suspicious of campaign finance limits and may be poised to deregulate elections even further.

Oral arguments in McCutcheon v. Federal Election Commission reinforced the conventional wisdom that Chief Justice John G. Roberts Jr. will decide the case, which challenges the constitutionality of the aggregate campaign contribution limit.

Roberts gave no obvious clues as to which direction he will tilt, but his questions made clear that he takes seriously Alabama businessman Shaun McCutcheon’s assertion that the limit violates his First Amendment rights. The overall limit bars any individual from giving more than $123,200 to PACs, parties and candidates in a single election cycle.

Roberts closely questioned Solicitor General Donald B. Verrilli, Jr., who defended the contribution limit on behalf of the FEC and who argued that the aggregate cap blocks donors from circumventing the “base” contribution on direct donations to candidates. The aggregate limit serves as “a bulwark against the reality and appearance of corruption,” Verrilli told the court.

A donor could get around that base limit, which stands at $2,600 per election, by contributing that amount to multiple state and national parties with the understanding that it would go to a limited number of candidates, Verrilli argued. With no aggregate limit, a contributor could give out as much as $3.6 million in a single election by donating the maximum to PACs, parties and candidates, he noted.

But Roberts appeared skeptical. The aggregate limit “seems to me a very direct restriction on much smaller contributions,” the chief justice said. As an analogy, he observed that “you could not have a rule that says The [Washington] Post or The New York Times can only endorse nine candidates.” Roberts also asked whether there might be other means, such as barring transfers between candidates or committees, to prevent contributors from circumventing base contribution limits.

Roberts is considered decisive because Justices Anthony M. Kennedy, Clarence Thomas and Antonin Scalia have already signaled in previous cases that they believe contribution limits should be subject to the same strict constitutional scrutiny as campaign expenditures.

Lawyer Bobby R. Burchfield made that very case before the high court today on behalf of Senate Minority Leader Mitch McConnell, R-Ky., who was granted 10 minutes to testify during oral arguments.

“Sen. McConnell believes that all restrictions of this nature should be reviewed under strict scrutiny,” Burchfield told the court. He also argued that aggregate limits weaken political parties in comparison with independent, unrestricted PACs, which are no longer subject to spending limits in the wake of the court’s 2010 Citizens United v. FEC ruling.

“In the current environment, national political parties are being marginalized by outside groups,” Burchfield said.

Scalia concurred. Referring to the aggregate limit, he asked: “Isn’t the consequence of the provision to sap the vitality of the political parties” and to encourage what might be called “drive-by PACs?”

The case could dramatically reorder the campaign finance system. Should the high court concur with McConnell that all contribution limits are constitutionally suspect and should be subject to strict scrutiny, the base limits could be vulnerable to constitutional challenge.

The case also tests whether the court is prepared to define corruption in narrow terms, involving only a quid-pro-quo exchange of money for votes, or will uphold the broader understanding of corruption set by such cases as McConnell v. FEC, which sustained the 2002 ban on unrestricted “soft” money. Verrilli said the principle established in McConnell applies here, because a political leader soliciting a check in the millions would invariably experience indebtedness to the donor.

Justice Sonia Sotomayor took up this argument in her line of questioning, describing how so-called joint fundraising committees, which typically allow party committees and candidates to raise money in tandem, could collect $100,000 or more from one donor and direct it to a single candidate. Sotomayor and Justice Stephen G. Breyer closely questioned lawyer Erin Murphy, who argued on behalf of McCutcheon.

Under such a scenario, “this candidate knows all of his $100,000 donors,” said Sotomayor. Murphy interjected: “But they’re not actually donors to him at that point.” To which Sotomayor replied that the $100,000 would be “20 times what the individual limits allow.”

Scalia called such hypotheticals “fanciful” and commented that, given how much money is spent on elections, the $3.6 million Verrilli described is not “a lot of money.” Scalia also dismissed the notion that simply soliciting large amounts of money would invite corruption, asking: “If gratitude is corruption, don’t these independent expenditures evoke gratitude?”

In response, Sotomayor quipped that, if the court is having second thoughts about its ruling (in Citizens United) that independent campaign expenditures are not corrupting, “we could change that part.” No one expects the high court to reverse that ruling, of course. If anything, today’s arguments revealed that the court’s conservative majority remains reluctant to defend campaign finance restrictions of any kind.